Metabolic Pathways Flashcards
Metabolic pathways are
integrated and controlled reactions within a cell
Metabolic pathways are reactions controlled by
presence or absence of enzymes which act as catalysts
In animals, specific metabolic pathways can produce
vitamins and haemoglobin
Metabolic pathways are a series of reactions that
start with a substrate
finish with end product
Anabolic
requires energy
build up large molecules from smaller ones (biosynthesis)
Catabolic
releases energy
break down large molecules into smaller ones (degradation)
example of anabolic reaction
synthesis of glycogen from glucose
example of catabolic reaction
process of food digestion, where different enzymes break down food particles so they can be absorbed by small intestine
Metabolic pathways can be
reversible and irreversible
most are reversible
All metabolic pathways have to be regulated and controlled to…
Stop build up of an end products that isnt needed
Active site has
high affinity to substrate as well as being specific to substrate, this orientates reactants into correct position for reaction to take place
Binding of enzyme to substrate does what?
lowers activation energy of reaction
rate of enzyme reaction can be affected by?
substrate concentration
As substrate concentration increases
enzyme reaction increases until all active sites are occupied by substrates, then all active sites are occupied, enzyme is saturated
When all active sites are occupied, the enzyme is said to be?
Saturated
At point of saturation, adding more substrates…
Makes no difference to reaction rate
Inhibitors
can be used to stop enzyme binding to substrate - as a result inhibitors can directly control progress of metabolic pathway
3 types of inhibition
Competitive
Non-competitive
Feedback
Competitive Inhibition
Occurs when an inhibitor molecule binds to active site of enzyme
Stops substrate from binding
compete with substrate because have similar molecular shape
How to reverse competitive inhibition
Increase substrate concentration
Substrate eventually dilutes inhibitor so all enzyme molecules bind to substrate
Example of competitive inhibitor
Sarin
Non-competitive inhibition
An inhibitor does not bind to active site bit binds to a different part of enzyme, this changes the active site shape, this stops substrate binding to enzyme and decreases reaction rate
Example of non-competitive inhibitors
cyanide, mercury or silver
Graph of inhibitors
Steep and high - no inhibitor
slower but same end height - competitive inhibitor
slower and lower - competitive inhibition
Feedback inhibition
End product in a metabolic pathway binds to an enzyme at start of pathway
Negative feedback process
Stops metabolic pathway and so prevents further synthesis of end product until end product concentration decreases. Higher concentration of end product, quicker metabolic pathways stops